- Dec 19 Dec 19 8:00AMEAS PhD Dissertation Defense by Dipshika Das
EAS PhD Dissertation Defense by Dipshika Das Date: December 19, 2023 Time: 8:00 a.m. Topic: Enhanced Ammonium Removal and Recovery Using Alkaline Hydrothermally Treated Chabazite (CHA) Zeolite Zoom: https://umassd.zoom.us/j/91948495335?pwd=TjFnS1N1RmIyNGV0cDVRK25rdGdVdz09 Meeting ID: 919 4849 5335 Passcode: 161289 Abstract: Natural zeolites, as inorganic ion exchangers, exhibit a strong affinity for ammonium (NH4+), rendering them promising candidates for efficient NH4+ removal from municipal/industrial wastewater and agricultural runoff. The ability to recover NH4+ during zeolite regeneration contributes to a circular economy, significantly reducing the energy footprint associated with NH4+ generation. Alkaline hydrothermal treatment of natural zeolites enhances their ion-exchange capacity by incorporating extra-framework cations into their crystal structures. In this study, Chabazite (CHA), a natural zeolite, underwent alkaline hydrothermal treatment with varying alkali concentration, temperature, and treatment duration. A comprehensive analytical investigation, including X-ray Powder Diffraction (XPD), Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and 27Al and 29Si Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR), conclusively demonstrated the conversion of CHA into analcime (ANA), a zeolite with a denser tetrahedrally coordinated atom structure. Mesopores in a zeolite act as an entrance for larger molecules, facilitating their movement for catalytic chemical reactions. This modification enhances the ion exchange capacity of zeolite, improves mass-transfer and opens up more accessible sites in the zeolite. This study provides conclusive evidence of enhanced mesoporosity of CHA following alkaline hydrothermal treatment. The modified zeolite exhibited twice the NH4+ removal capacity compared to the parent natural CHA. When utilized in a packed-bed configuration, the modified CHA demonstrated excellent selectivity toward NH4+ in synthetic wastewater containing competing cations. The exhausted zeolite was successfully regenerated using a brine solution, recovering 94 - 98% of the loaded NH4+, providing a nitrogen-rich source for various applications. The regenerated zeolite could be used for subsequent exhaustion cycle without any loss of performance. Keywords: Ion-exchange, Ammonium, Chabazite, Alkaline mediated hydrothermal treatment, Selectivity, Cation Exchange Capacity, Regeneration ADVISOR(S): Dr. Sukalyan Sengupta, Dept of Civil & Environmental Engineering (firstname.lastname@example.org) COMMITTEE MEMBERS: Dr. Walaa Mogawer, Dept of Civil & Environmental Engineering Dr. Jonathan Mellor, Dept of Civil & Environmental Engineering Dr. Chen-Lu Yang, Center for Innovation & Entrepreneurship, UMass Dartmouth Dr. Sudipta Sarkar, Indian Institute of Technology, Roorkee, India NOTE: All EAS Students are ENCOURAGED to attend.
- Dec 19 Dec 19 10:00AMEAS Doctoral Proposal Defense by Shabnam Mohammadshahi
EAS Doctoral Proposal Defense by Shabnam Mohammadshahi Date: Tuesday, December 19, 2023 Time: 10am Topic: Drag Reduction and Plastron Stability of Super-Hydrophobic Surfaces in Turbulent Flows Location: SENG 108 Abstract: The hydrodynamic skin friction in turbulent flows contributes to 60-70% of the total drag of most surface and subsurface vessels. Applying Super Hydrophobic Surface (SHS) is a new passive method to reduce the friction drag in turbulent flows, due to its ability to trap a layer of gas bubbles (or plastrons) within the surface micro-structures. However, the application of SHS in real engineering systems, e.g., marine vessels, is still a challenge for the reason that the SHS may lose the gas bubbles and the drag-reducing property under turbulent flows. It is unclear what is the optimal surface texture for achieving sustained drag reduction by SHS. To address these challenges, this dissertation proposal has three contributions: (i) development of a simple method to fabricate SHSs with different surface roughness; (ii) evaluation of the impact of surface roughness on the friction drag of SHS in turbulent flows; and (iii) development of novel optical methods to investigate the flow-induced deformation of the gas-liquid interface on SHS. First, we developed a novel method to fabricate SHSs with different roughness heights based on superimposing nanosized hydrophobic silica particles on top of the sandpapers. The surface roughness was changed by simply using sandpapers of different grit sizes. We found that the coated sandpapers with grit sizes of 240, 400, 800, 1000, and 1500 exhibited super-hydrophobicity, while other coated sandpapers with grit sizes of 60, 120, and 600 did not show superhydrophobicity for the reason that the Cassie-Baxter state was not stable. The fabricated SHS remained in the partial Cassie-Baxter state at the highest pressure (2.4 atm), although the percentage of surface area covered by gas reduces with increasing pressure. Then, the drag-reducing properties of fabricated SHSs were measured in a fully developed turbulent channel flow facility. The mean flow velocity varied from 0.45 to 4 m/s, and the Reynolds number, based on the channel height and mean flow velocity varied from 2,900 to 24,500. The wall friction and drag reduction of the SHSs were measured based on the pressure drops in the fully developed region. We found the slip length of SHS reduces as increasing Reynolds number due to the increase of roughness effect and the reduction of surface area covered by gas. A maximum 47% drag reduction was obtained by the fabricated SHSs in turbulent flows. Moreover, we found that the drag reduction of SHS increases with reducing the roughness height (i.e., increasing the grit size of the sandpaper). Finally, we developed novel optical methods to measure the gas-liquid interface on SHS in turbulent flows. Understanding the dynamics of the interface on SHS is critical to design robust SHS that can survive in strong turbulent flows. For interface on non-transparent SHS (e.g., coated sandpapers), we used a reflected light microscope. For an interface on transparent SHS (e.g., patterned PDMS surface), we used a Reflection Interference Contrast Microscopy which has the capability to resolve 3D interface shape. Preliminary data of the interface status in turbulent flows have been obtained, which showed a reduction of surface area covered by gas as increasing Reynolds number. Future work of this Ph.D. thesis will include velocity measurement by particle-image-velocimetry and interface deformation measurement by high-speed imaging. ADVISOR(S): Dr. Hangjian Ling, Department of Mechanical Engineering (email@example.com) COMMITTEE MEMBERS: Dr. Banafsheh Seyedaghazadeh, Dept of Mechanical Engineering Dr. Caiwei Shen, Dept of Mechanical Engineering Dr. Geoffrey W. Cowles, Dept of Marine Science & Technology NOTE: All EAS Students are ENCOURAGED to attend.
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- Dec 20 Dec 20 10:00AMEAS Doctoral Proposal Defense by Hadi Samsamkhayani
Topic: Experimental Study on Fluid-Structure-Surface Interactions of Streamlined Structures Location: SENG 110 Material Science Lab Abstract: Flow-induced vibration (FIV) occurs when fluid interacts with a flexible body, causing oscillation due to fluctuating forces from vortex shedding. Flow-induced vibration can affect the performance, safety, and reliability of various engineering systems, such as bridges, pipelines, wind turbines, offshore structures, etc. The FIV response of these systems can be significantly influenced by asymmetry, which can be either geometric or flow-dependent. Previous studies have investigated the relationship between bluff bodies and the free surface, showing that as the submerged height of the structure decreases, the FIV response changes considerably. Despite extensive FIV studies on geometric asymmetries, such as the asymmetric boundary condition of the structure, cross-section, and various angles of attack, the influence of flow asymmetry has not been as thoroughly investigated. For a structure submerged in water, it can experience asymmetric flow when placed near the interface of water and air (free surface). The deformable free surface can act as an elastic member that can create an additional coupling between the structure and the flow, which introduces what we term "fluid-structure-surface interactions". Understanding these interactions in submerged hydrodynamic streamline bodies is crucial for a wide variety of applications, ranging from near-surface energy harvesting to the design of marine structures and tidal power generation equipment. The majority of studies exploring the influence of free surface on streamlined structures have focused on the theoretical and computational examination of two-dimensional stability conditions. Few experimental studies have examined the impact of the free surface on the response of foils and plates in prescribed motion. To our knowledge, no previous study has visually quantified the characteristics of three and two-dimensional asymmetric flow in self-excited oscillating plates or foils. The aim of this research is to investigate how the proximity to the deformable free water surface affects the dynamic hydroelastic and hydrodynamic behavior of a flexible plate. To achieve this goal, we initially examined the flow dynamics surrounding a stationary rigid flat plate placed near a free surface, at varying angles of attack (AOA), Reynolds numbers, and submerged depths. Later on, flow structure and subsequent FIV response of the plate, with one degree of freedom (DoF) in the plunging direction in terms of amplitude and frequency of oscillation was investigated at various AOA. In the subsequent stage, we expanded our investigation to plates with both 1DoF and 2DoF for pitching and plunging oscillations, conducting experiments at various submerged heights adjacent to the free surface. These findings represent a crucial step towards achieving the ultimate objective of this research: understanding FIV in flexible films in close proximity to the air-water interface. We conducted a series of well-controlled lab experiments using a re-circulating water tunnel tests. In these experiments, we used a rigid flat plate fabricated from transparent acrylic. To capture pitching and plunging oscillations, we used a Miniature Rotary Magnetic Encoder and a laser displacement sensor, respectively. Our analysis involved studying the structural response of the system in terms of oscillation amplitude and frequency. We also investigated the vortex dynamics using a combination of qualitative and quantitative flow visualization techniques, including Hydrogen Bubble (HB), state-of-the-art time-resolved volumetric Particle Tracking Velocimetry (TR-PTV), and two-dimensional Particle Image Velocimetry (2D-PIV) methods. We further analyzed three and two-dimensional vortex dynamics in the wake of the structure by using techniques like proper orthogonal decomposition, phaseaveraged methods, and coherent structural analysis, such as Q and lambda criteria. ADVISOR(S): Dr. Banafshesh Seyed-Aghazadeh, Dept of Mechanical Engineering (firstname.lastname@example.org) COMMITTEE MEMBERS: Dr. Mehdi Raessi, Dept of Mechanical Engineering Dr. Hangjian Ling, Dept of Mechanical Engineering Dr. Geoffrey W. Cowles, Dept of Marine Science & Technology
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- Jan 10 Jan 10 10:00AMEAS PhD Dissertation Defense by Wen Jin (CSE Option/Mechanical Engineering)
EAS PhD Dissertation Defense by Wen Jin (CSE Option/Mechanical Engineering) DATE: January 10, 2024 TIME: 10:00 a.m. - 1:00 p.m. TOPIC: Computational investigation of impact of micron-sized water droplets onto freezing superhydrophobic surfaces and novel 3D numerical modeling of contact line pinning LOCATION: CSCDR - TXT 105 Zoom link: Please contact Dr. Raessi (email@example.com). ABSTRACT: This thesis presents a computational study on the impingement of micron-sized water droplets onto freezing superhydrophobic surfaces. In particular, the investigation is focused on the effect of surface wettability, temperature, droplet size and impact speed on the droplet dynamics and freezing behavior. A numerical approach based on the Volume-of-Fluid (VOF) method was employed to simulate the droplet-surface interaction and the droplet behavior during the freezing process. A theoretical model is presented for predicting the transition from bouncing to sticking after droplets impact freezing surfaces. The theoretical model, which relies on time scales of droplet spreading and droplet freezing, predicts the droplet behavior, i.e., bouncing off of or sticking to the freezing surface, as a function of substrate temperature and Weber number, which represents the ratio of inertia to surface tension. A constant in the theoretical model was determined based on a subset of simulation results obtained in this thesis. The theoretical model predictions were then verified using both experimental results of millimeter-sized drops and computational results of micron-sized droplets impacting freezing superhydrophobic surfaces, showing good agreements in both cases. In total, 720 simulations of droplet impact were performed to inform and validate the theoretical model. Moreover, a novel three-dimensional numerical scheme is developed for modeling discontinuous pinning along sharp straight edges. The proposed scheme is devised for multi-phase flow solvers that rely on the VOF method, although its fundamental concepts can be extended and applied to other methods. Following the Piecewise-Linear-Interface-Construction (PLIC) approach in VOF, the discontinuous pinning is modeled by adjusting the orientation of PLIC polygons located near a sharp edge according to the pinning stage. That is achieved by solving a root-finding problem and using a 3D geometrical toolbox, where the advancing contact angle determines critical volume fractions in numerical cells neighboring the sharp edge. Implementing the proposed scheme in our multi-phase flow solver, we assessed its performance using several test cases where contact line pinning effects dominate. To demonstrate the scheme's efficacy, we present quantitative comparisons of our results at various grid resolutions and with an experimental/theoretical study. Furthermore, we show quantitatively that without a numerical treatment of contact line pinning, the simulation results will be drastically different. Contact line pinning plays a critical role in several technologies including separation, lithography, lens fabrication, microfluidic flow control among numerous others. The proposed scheme will help to accurately capture the pinning effects in computational simulations of such applications. Acknowledgment: The research support from the National Science Foundation under CBET Grant No. 1336232 is gratefully acknowledged. ADVISOR: Dr. Mehdi Raessi (firstname.lastname@example.org, 508-999-8496), Dept of Mechanical Engineering COMMITTEE MEMBERS: Dr. Alfa Heryudono, Dept of Mathematics Dr. Hangjian Ling, Dept of Mechanical Engineering Dr. Jun Li, Dept of Mechanical Engineering Open to the public. All MNE and EAS students are encouraged to attend. For questions contact Dr. Mehdi Raessi (email@example.com, 508-999-8496)
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- Jan 16 Jan 16 10:00AMCharlton College of Business Graduate Programs Virtual Information Session
A virtual information session on the graduate business programs at UMass Dartmouth. - Explore various business graduate programs - Find out how you can complete your degree at your pace - Discover how you can concentrate in a field that meets your interests and career goals - Learn about Charlton's more flexible GMAT waivers - Understand the value of Charlton College of Business degree - Hear about the next steps to enrollment This event designed to answer questions you may have about the various degree and certificate programs.
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- Jan 26 Jan 26 8:30AM22nd Annual Rev. Dr. Martin Luther King, Jr. Breakfast
Featuring Key Note Speaker Theo E.J. Wilson is a founding member of the Denver Slam Nuba team, who won the National Poetry Slam in 2011. He's also known as The New Black Klansman. He began his speaking career in the N.A.A.C.P. at the age of 15, and he has always had a passion for social justice.
- Apr 9 Apr 9 3:30PM2nd Annual Mock Law Class and Pre-Law End of the Year Celebration
Join UMass Dartmouth Pre-Law, Pre-Law Society and UMass Law for the 2nd annual Mock Law Class. An end of the year celebration will also be held for graduating seniors. Contact UMass Dartmouth Pre-Law for more information at firstname.lastname@example.org.
Claire T. Carney Library, Room 122, Grand Reading Room
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